Down hole bypass valve

ABSTRACT

The invention relates to bypass valves for use in wellbores, particularly but not exclusively to bypass valves used during the setting of hydraulic anchor packers. The invention provides a bypass valve for selectively isolating the interior of a down-hole assembly from the exterior thereof, the bypass valve comprising guide pin in received slot being adapted to permit movement of a piston (30) from a first position to a second position in response to a predetermined pressure differential between a bore (58) of the piston (30) and the exterior of a body (4) but normally preventing movement of the piston (30) to a third position in which the bore (58) of the piston (30) is substantially isolated from the exterior of the body (4), and an extension of the guide slot for overriding the guide pins in the slot, so as to permit movement of the piston (30) to the third position. The invention thereby provides a bypass valve which resists any tendency to close prematurely and which communicates any such tendancy to the surface.

The invention relates to bypass valves for use in wellbores,particularly but not exclusively to bypass valves used during thesetting of hydraulic anchor packers.

The drilling industry often has the need to monitor the axial positionand angular orientation of a tool (such as a whipstock) within awellbore, and to rigidly secure the tool within the wellbore once arequired position and orientation has been achieved. The position andorientation of a tool may be determined by using a MWD orMeasurement-While-Drilling tool. An MWD tool requires a flow of wellborefluid through a drill string in order to communicate a measured positionand orientation to the surface. The flow rates required are oftensufficiently high to generate a pressure drop between the inside and theoutside of the drill string to prematurely set the hydraulic anchorpacker.

To overcome this problem, drill strings are often provided with a bypassvalve located between the MWD tool and the anchor packers. When theposition and orientation of the drill string is being monitored,wellbore fluid is pumped through the MWD tool via the bore in the drillstring. The bypass valve prevents the setting of the anchor packers byallowing the wellbore fluid flowing downhole of the MWD tool to passinto the wellbore annulus. The fluid pressure differential across thehydraulic anchor packer is thereby maintained below the settingpressure.

Once the required drill string position and orientation is obtained, thehydraulic anchor packer is set by increasing the flow rate of thewellbore fluid down the drill string. The increase in flow rate resultsin an associated increase in dynamic pressure. Once the dynamic pressureincreases to a predetermined magnitude, the bypass valve is activatedand the fluid path between the wellbore annulus and the drill stringbore is closed. The wellbore fluid is thereby directed downhole to theanchor packers where the appropriate setting pressure (typically a1500-3000 psi differential between the inside and outside of the anchorpacker) is then applied.

A conventional bypass valve incorporates a piston which slides within acylinder in response to dynamic wellbore fluid pressure. The wall of thecylinder is provided with a plurality of holes through which fluid maypass from the drill string bore to the wellbore annulus. The piston isheld in an open position by biasing means, such as a spring or a shearpin, or a combination of both. When the appropriate dynamic pressure isachieved, the biasing means is overcome and the piston slides within thecylinder so as to sealingly close the plurality of holes.

This type of bypass valve can be problematic when the wellbore fluidwithin the drill string carries a large amount of debris. This debrismay be either pumped from the surface by accident, produced by componentfailure in the MWD tool or generated during the drilling of thewellbore. The debris can accumulate on the piston and increase the forceexerted on the piston by any given flow rate of wellbore fluid. Incertain circumstances, the accumulation of debris can be sufficient tocause the bypass valve to close prematurely. This in turn causes apremature setting of the hydraulic anchor packers. Premature setting canalso occur if the piston biasing means in the bypass valve fails.

It is an object of the present invention to provide a bypass valve foruse in a wellbore which resists any tendency to close prematurely andwhich communicates any such tendency to the surface.

The present invention provides a bypass valve for selectively isolatingthe interior of a down-hole assembly from the exterior thereof, thebypass valve comprising: a body incorporating a wall provided with atleast one opening extending therethrough; a piston slidably mounted inthe body; a longitudinal bore extending through the piston; a firstposition of the piston relative to the body establishing a passage fromthe bore of the piston to the exterior of the body via the opening; asecond position of the piston relative to the body establishing arestricted passage from the bore of the piston to the exterior of thebody via the opening; a third position of the piston relative to thebody substantially isolating the bore of the piston from the exterior ofthe body; constraining means for controlling movement of the pistonbetween the first, second and third positions, the constraining meansbeing adapted to permit movement of the piston from the first positionto the second position in response to a predetermined pressuredifferential between the bore of the piston and the exterior of the bodybut normally preventing movement of the piston to the third position;and overriding means for overriding the constraining means so as topermit movement of the piston to the third position.

The piston is preferably biased to the first position by means of aspring. Furthermore, the piston may incorporate a wall provided with atleast one opening extending therethrough so that, in the first positionthe openings of the piston and body are in register, and in the secondposition the openings of the piston and the body are partly in register.

Preferably the constraining means comprises a guide pin and a guide slotfor receiving the guide pin. The guide slot is preferably provided aboutthe outer peripheral surface of the piston and extends in a directionhaving one component parallel to the direction of axial movement of thepiston. The overriding means may be provided by an extension of theguide slot.

Preferably the guide pin is fixedly located relative to the body and theguide slot is formed in the exterior surface of the piston.

Connecting means may be provided for connecting a nozzle to the piston.Furthermore, a filter may be provided adjacent the or each opening ofthe body. It may also be desirable to provide a filter for filtering afluid flowing into the bore of the piston.

The bypass valve provided by the present invention has the advantageover the conventional bypass valves of not closing prematurely due tothe presence of debris in the drill string or the failure of the meansbiasing the bypass valve to the open position. An appropriateaccumulation of debris or a failure of the biasing means results in themovement of the bypass valve to a partially closed position in whichwellbore fluid is still able to flow to the wellbore annulus. The flowarea through the bypass valve is thereby reduced which leads to apressure rise of approximately 300-600 psi experienced at the surface.This pressure rise provides an indication that the bypass valve hasattempted to close prematurely, but is not sufficient to set the anchorpackers. The warning received by way of the pressure rise may be actedupon by taking remedial action such as decreasing the flow rate ofwellbore fluid down the drill string. The position and orientation ofthe drill string may continue to be adjusted even though the bypassvalve has attempted to close prematurely.

Embodiments of the present invention will now be described withreference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional side view of a first embodiment of thepresent invention;

FIG. 2 is a plan view of the unwrapped profile of the guide slot of thefirst embodiment of FIG. 1;

FIG. 3 is a cross-sectional view of the first embodiment of FIG. 1 takenalong line A--A;

FIG. 4 is a large scale cross-sectional side view of the firstembodiment of FIG. 1;

FIG. 5 is a cross-sectional side view of a second embodiment of thepresent invention; and

FIG. 6 is a plan view of the unwrapped profile of the guide slot of thesecond embodiment of FIG. 5.

A first embodiment of the present invention is shown in FIG. 1. Theembodiment of FIG. 1 is a bypass valve defined by a plurality ofinternal parts mounted within a shell 2.

The shell 2 comprises a casing 4 threadedly connected to a crossovermember 6. The upper end 8 of the crossover member 6 is provided with aninternal screw thread 10. Assemblies to be arranged up-hole of thebypass valve are connected to the crossover member 6 by means of theinternal screw thread 10. The lower end 12 of the casing 4 is providedwith an external thread 14. Assemblies to be arranged down-hole of thebypass valve are connected to the casing 4 by means of the externalthread 14. The casing 4 and the crossover member 6 define a bore 16 inwhich the internal parts of the bypass valve are located. The portion ofthe bore 16 defined by the casing 4 is provided with a shoulder 18 whichprevents undesirable axial movement of the internal parts towards thelower end 12. Four vent holes 20 are provided in the casing 4 which arearranged coplanar, up-hole of the shoulder 18 and equispaced about thecircumference of the bore 16. The vent holes 20 allow fluid to eitherenter the bypass valve from the wellbore annulus or enter the wellboreannulus from the bypass valve. Each vent hole 20 is provided with afilter disc 22 held in position by means of a filter disc circlip 24.The arrangement of the vent holes 20 is shown in FIG. 3.

The plurality of internal parts include a seal housing 26, a sleeve 28,a piston 30, an internal filter 32 and an adjusting ring 34. The sealhousing 26 is substantially cylindrical in shape and has an outerdiameter similar to the diameter of the bore 16 defined by the portionof the casing 4 up-hole of the shoulder 18. The seal housing 26 islocated down-hole of the vent holes 20 and is arranged so as to abut theshoulder 18.

The sleeve 28 is also substantially cylindrical in shape, the upper endthereof having an outer diameter similar to that of the seal housing 26.The lower end 36 (see FIG. 4) of the sleeve 28 has an outer diameterwhich is less than that of the seal housing 26. The sleeve 28 isarranged within the casing 4 with the lower end 36 of the sleeve 28located in abutment with the seal housing 26. A vent chamber 38 in fluidcommunication with the vent holes 20 is thereby defined by the lower end36 of the sleeve 28, the seal housing 26 and the casing 4. FIG. 3 showsthat the vent chamber 38 defines an annulus shape and is located betweenthe sleeve 28 and the casing 4. The vent chamber 38 is also in fluidcommunication with a plurality of vent chamber ports 40. The ventchamber ports 40 are provided in the form of slots located in a recess47 defined the lower end 36 of the sleeve 28.

The upper end of the sleeve 28 is provided with two guide pin holes 41,43 which are arranged on opposite sides of the sleeve 28. Guide pin 42,44 are a push fit within the bores 41, 43 and are provided with blindscrew threaded recesses for receiving an extractor tool. The guide pins42, 44 extend from the inner surface 46 of the sleeve 28.

The piston 30 is located in abutment with the inner surface 46 of thesleeve 28 and the inner surface 48 of the seal housing 26. Thearrangement is such that the piston 30 may rotate and move axiallywithin the sleeve 28 and the seal housing 26. The upper end 50 of thepiston 30 is provided with a guide slot 52 in which the guide pins 42,44 are located. The guide slot 52 has an unbroken profile defined aroundthe circumference of the upper end 50 of the piston 30. The unwrappedprofile of the guide slot 52 is shown in FIG. 2. The location of theguide pins 42, 44 in the guide slot 52 limits the movement of the piston30 relative to the sleeve 28. The lower end 54 of the piston 30 extendsbeyond the vent chamber ports 40 and is provided with a plurality ofpiston holes 56 in the form of elongated slots. The piston holes 56allow wellbore fluid to pass from the vent chamber 38 to a piston bore58 defined by the piston 30. The upper end 50 of the piston 30 is alsoprovided with connecting means 60 which allow the attachment of anappropriate nozzle (not shown) to the piston 30 so as to effectivelyreduce the diameter of the piston bore 58. The attachment of a nozzle tothe piston 30 reduces the flow rate of wellbore fluid required to movethe piston 30 axially within the sleeve 28. The flow rate at which thebypass valve closes may therefore be varied with the inclusion of asuitable nozzle.

The piston 30 and the sleeve 28 define a piston spring chamber 62 inwhich a piston spring 64 is located. The piston spring 64 abuts thelower end 36 of the sleeve 28 and the upper end 50 of the piston 30, andis arranged so as to bias the piston 30 towards the upper end 8 of thecrossover member 6. A ball bearing assembly 66 is provided between thepiston spring 64 and the upper end 50 of the piston 30 so as to reduceto a minimum any transfer of torque from the piston 30 to the pistonspring 64. Axial movement of the piston 30 is assisted by the venting ofthe piston spring chamber 62 to the vent chamber 38 by means of pistonspring chamber ports 68. The piston spring chamber ports 68 take theform of holes provided in the lower end 36 of the sleeve 28 providingfluid communication between the piston spring chamber 62 and the ventchamber 38. The axial movement of the piston 30 is restricted by apiston stop 70 and a piston circlip 72, and also by the location of theguide pins 42, 44 within the guide slot 52.

The internal filter 32 is located up-hole of the piston 30 between thesleeve 28 and the adjusting ring 34. The internal filter 32 is capableof filtering debris having a dimension greater than 1/8 inch. Theadjusting ring 34 extends up-hole of the internal filter 32 so as toabut the crossover member 6. Seals 74 are provided in order to preventundesirable ingress of wellbore fluid. Glyd ring seals 76, 77 are alsoprovided to assist with the movement of piston 30 within the sleeve 28and the seal housing 26.

The components of the bypass valve are manufactured from a suitablegrade of steel. The interfacing portions of the lower end 36 and thepiston 30 are coated with tungsten carbide so as to improve the wearresistant characteristics of the bypass valve. The glyd ring seals aremanufactured from PTFE. Alternative materials will be apparent to areader skilled in the art.

The bypass valve of FIGS. 1, 2, 3 and 4 is assembled by sliding thepiston stop 70, the piston spring 64, the ball bearing assembly 66 andthe piston 30 into the sleeve 28. The piston circlip 72 is then locatedin position so as to prevent the piston spring 64 from pushing thepiston 30 from the sleeve 28. The guide pins 42, 44 are located withinthe guide slot 52 by aligning the guide pin holes 41, 43 with the guideslot 52 and then screwing the guide pins 42, 44 into the guide pin holes41, 43. A piston assembly is thereby defined. The seal housing 46, thepiston assembly, the internal filter 32 and the adjusting ring 34 arethen slid into the casing 4. The crossover member 6 is then threadedlyconnected to the casing 4. The crossover member 6 abuts the adjustingring 34 so as to press the adjusting ring 34, the internal filter 32,the sleeve 28 and the seal housing 26 against the shoulder 18. Movementof the sleeve 28 relative to the casing 4 is thereby prevented.

The operation of the bypass valve will now be described with referenceto a drill string incorporating an MWD tool, the bypass valve, awhipstock and a hydraulic anchor packer.

FIGS. 1, 2, 3 and 4 show the bypass valve in an open configuration inwhich the piston holes 56 are directly aligned with the vent chamberports 40. In this configuration, wellbore fluid is able to flow from thepiston bore 58 to the wellbore annulus, or vice versa. The bypass valveis arranged in an open configuration when the guide pins 42, 44 arelocated at positions A, C or E within the guide slot 52.

The bypass valve is run into a wellbore arranged in an openconfiguration. In so doing, wellbore fluid enters the drill stringthrough the vent holes 20. Debris, such as drill cuttings, is preventedfrom entering the drill string by means of the filter discs 22. Thefilter discs 22 comprise a plurality of holes small enough to preventthe passage therethrough of any debris likely to hinder the operation ofthe bypass valve or any other part of the drill string. The flow ofwellbore fluid into the bypass valve equalises the very high hydrostaticpressures exerted on the outer surface of the drill string.

The wellbore fluid held within the drill string is circulated down thedrill string bore at a predetermined flow rate. The flow rate issufficient for the operation of the MWD tool, but not high enough togenerate the dynamic pressure required to activate the bypass valve.Consequently, wellbore fluid is pumped from the surface, through the MWDtool, into the wellbore annulus via the vent holes 20, and up thewellbore annulus to the surface. The hydraulic anchor packers are notthereby exposed to the required setting pressure differential.

The risk of premature activation of the bypass valve is reduced by theinternal filter 32. The internal filter 32 reduces the likelihood ofdebris accumulating on the piston 30 and blocking the piston bore 58. Inconventional bypass valves, debris accumulation can readily occurresulting in an increase in the force exerted on the bypass valve pistonat any given flow rate. If the debris accumulation on the piston issevere, then the piston of a conventional bypass valve can moveunexpectedly. Premature setting of the anchor packer may result.Although the internal filter 32 reduces the risk of this occurring, itis possible for very fine debris to still accumulate on the piston 30.If sufficient debris accumulates, then piston 30 may be unexpectedlymoved towards a closed position in which the piston 30 prevents the flowof wellbore fluid through the vent holes 20. The piston 30 may also movein this manner if the piston spring 64 fails.

Movement of the piston 30 relative to the sleeve 28 is restricted by thelocation of the guide pins 42, 44 within the guide slot 52. If thepiston 30 unexpectedly moves towards a closed position, then the guidepins 42, 44 move from position A within the guide slot 52 to position B.In so doing, the piston 30 rotates within the sleeve 28 and movesaxially to a part closed position in which the piston holes 56 are notaligned with the vent chamber ports 40, but are in fluid communicationwith the vent chamber ports 40 by means of the recess 47. Axial movementof the piston 30 is assisted by a venting of wellbore fluid from thespring chamber 62 via the piston spring chamber ports 68. The movementof the piston 30 into the part closed position generates a pressure riseof approximately 300-600 psi which may be measured at the surface. Thepressure rise is sufficient to provide a clear indication at the surfacethat the bypass valve has moved into a part closed configuration, butnot sufficient to generate the pressure differential of 1500-3000 psirequired to set the hydraulic anchor packer.

If a pressure rise of approximately 300-600 psi is measured at thesurface, then it is likely that the bypass valve has moved into a partclosed configuration due to debris accumulation on the piston 30 orfailure of the piston spring 64. Appropriate remedial action may then beundertaken. Such action may involve reducing the flow rate of wellborefluid down the drill string bore. Provided the piston spring 64 has notfailed, the piston spring 64 will then push the piston 30 back to anopen position. In so doing, the guide pins 42, 44 move from position Bto position C within the guide slot 52.

Once the required position and orientation of the whipstock has beenobtained, the hydraulic anchor packer is set by moving the bypass valveinto a closed configuration. In the closed configuration, the pistonholes 56 are located down-hole of the seal 77 so as to prevent the flowof wellbore fluid between the piston bore 58 and the wellbore annulus.The bypass valve is closed by cycling the piston 30 so that the guidepins 42, 44 locate in position F within the guide slot 52. This isachieved by stopping the flow of wellbore fluid down the drill stringbore to ensure that the guide pins 42, 44 are located at one ofpositions A, C or E within the guide slot 52 by the action of thespring. The flow rate is then increased to move the piston 30 axiallyand thereby move the guide pins 42, 44 to one of positions B, D or F.The process is repeated as necessary until the guide pins 42, 44 locatein position F within the guide slot 52. In this position, the piston 30sealingly closes the vent chamber ports 40. The required settingpressure differential is then generated at the anchor packer. Themovement of the piston 30 into the closed position produces a largepressure rise at the surface which may serve as an indication that theanchor packers have been set. This may be confirmed by attempting tomove the drill string within the wellbore.

A second embodiment of the present invention is shown in FIGS. 5 and 6.FIG. 5 shows a split view of a piston 130. The top half of the figureshows the piston 130 in an open position, and the bottom half of thefigure shows the piston 130 in a closed position.

The upper end 150 of the piston 130 is provided with a guide slot 152 inwhich one guide pin 142 is located. The guide slot 152 has a number ofcircumferential portions 153. Each circumferential portion 153 extendsperpendicularly to the axial direction in which the piston 130 moves.The internal surface 155 of the piston 130 is provided with an internalbore thread 157. The wellbore fluid flowing through the piston bore 158interacts with the internal bore thread 157 so as to impart a torqueonto the piston 130. The torque tends to rotate the piston 130 so thatthe guide pin 142 slides along the circumferential portions 153 of theguide slot 152.

Torque can be most efficiently imparted onto the piston 130 by providingan internal bore thread 157 which generates a "spiral staircase" type offluid flow. The internal bore thread 157 may be provided by casting theinternal surface 155 of the piston 130 using a male spiral moulding corepiece. Alternatively, a "spiral staircase" fluid flow could be generatedby locating a rod, provided with a female thread, within the piston bore158. A spiral flow is thereby generated about the rod.

The operation of the second embodiment is similar to that of the firstembodiment.

Further variations and alternatives will be apparent to a reader skilledin the art. For example, the internal filter 32 could be replaced, oradded to, by inserting a three to four foot long standard drill pipefilter into a housing attached to the bypass valve assembly. The longlength of the tubular filter pipe allows debris to collect without asignificant pressure rise. Furthermore, the guide slot may be altered sothat the piston must pass through an alternative number of part closedpositions before moving to a fully closed position.

We claim:
 1. A bypass valve for selectively isolating the interior of a down-hole assembly from the exterior thereof, the bypass valve comprising: a body incorporating a wall provided with at least one opening extending therethrough; a piston slidably mounted in the body; a longitudinal bore extending through the piston; a first position of the piston relative to the body establishing a passage from the bore of the piston to the exterior of the body via the opening; a second position of the piston relative to the body establishing a restricted passage from the bore of the piston to the exterior of the body via the opening; a third position of the piston relative to the body substantially isolating the bore of the piston from the exterior of the body; constraining means for controlling movement of the piston between the first, second and third positions, the constraining means being adapted to permit movement of the piston from the first position to the second position in response to a predetermined pressure differential between the bore of the piston and the exterior of the body but normally preventing movement of the piston to the third position; and overriding means for overriding the constraining means so as to permit movement of the piston to the third position.
 2. A bypass valve as claimed in claim 1, wherein the piston is biased to the first position by means of a spring.
 3. A bypass valve as claimed in claim 1, wherein the piston incorporates a wall provided with at least one opening extending therethrough such that, in the first position the openings of the piston and the body are in register, and in the second position the openings of the piston and the body are partly in register.
 4. A bypass valve as claimed in claim 1, wherein the constraining means comprises a guide pin and a guide slot for receiving the guide pin.
 5. A bypass valve as claimed in claim 4, wherein the guide slot is provided about the outer peripheral surface of the piston and extends in a direction having one component parallel to the direction of axial movement of the piston.
 6. A bypass valve as claimed in claim 4, wherein the overriding means comprises an extension of the guide slot.
 7. A bypass valve as claimed in claim 4, wherein the guide pin is fixedly located relative to the body and the guide slot is formed in the exterior surface of the piston.
 8. A bypass valve as claimed in claim 1, wherein connecting means is provided for connecting a nozzle to the piston.
 9. A bypass valve as claimed in claim 1, wherein a filter is provided adjacent the or each opening of the body.
 10. A bypass valve as claimed in claim 1, wherein a filter is provided so as to filter a fluid flowing into the bore of the piston. 